Solid state light emitter with pumped nanophosphors for producing high CRI white light

Abstract

A solid state white light emitting device includes a semiconductor chip producing near ultraviolet (UV) electromagnetic energy in a range of 380-420 nm, e.g. 405 nm. The device may include a reflector forming and optical integrating cavity. Phosphors, such as doped semiconductor nanophosphors, within the chip packaging of the semiconductor device itself, are excitable by the near UV energy. However the re-emitted light from the phosphors have different spectral characteristics outside the absorption ranges of the phosphors, which reduces or eliminates re-absorption. The emitter produces output light that is at least substantially white and has a color rendering index (CRI) of 75 or higher. The white light output of the emitter may exhibit color temperature in one of the following specific ranges along the black body curve: 2,725±145° Kelvin; 3,045±175° Kelvin; 3,465±245° Kelvin; 3,985±275° Kelvin; 4,503±243° Kelvin; 5,028±283° Kelvin; 5,665±355° Kelvin; and 6,530±510° Kelvin.

1. A solid state light emitting device, comprising:
 a semiconductor chip for producing electromagnetic energy in a range of 380-420 nm; 
 a package enclosing the semiconductor chip and configured to allow emission of light as an output of the device; 
 at least one reflective surface within the package forming an optical integrating cavity, wherein the semiconductor chip is positioned and oriented so that at least substantially all direct emissions from the semiconductor chip reflect at least once within the cavity; 
 a light transmissive solid filling at least a substantial portion of the optical integrating cavity, wherein a surface of the light transmissive solid forms an optical aperture of the optical integrating cavity; 
 a plurality of doped semiconductor nanophosphors within the package enclosing the semiconductor chip, each of the doped semiconductor nanophosphors:
 including nanocrystals formed of semiconductor materials which are doped with an impurity, 
 being excited in response to electromagnetic energy in the range of 380-420 nm for re-emitting visible light of a different spectrum having substantially no overlap with absorption spectra of the doped semiconductor nanophosphors, and 
 for together producing visible light in the output of the device when the doped semiconductor nanophosphors are excited by electromagnetic energy from the semiconductor chip, 
 
 wherein:
 (a) the visible light output produced during the excitation of the doped semiconductor nanophosphors is at least substantially white; 
 (b) the visible light output produced during the excitation of the doped semiconductor nanophosphors has a color rendering index (CRI) of 75 or higher; and 
 (c) the visible light output produced during the excitation of the doped semiconductor nanophosphors has a color temperature in one of the following ranges:
 2,725±145° Kelvin; 
 3,045±175° Kelvin; 
 3,465±245° Kelvin; 
 3,985±275° Kelvin; 
 4,503±243° Kelvin; 
 5,028±283° Kelvin; 
 5,665±355° Kelvin; and 
 6,530±510° Kelvin, 
 
 the semiconductor chip is positioned and oriented relative to the light transmissive solid so that any electromagnetic energy reaching the optical aperture surface of the light transmissive solid directly from the semiconductor chip impacts the optical aperture surface at a sufficiently small angle as to be reflected back into the optical integrating cavity by total internal reflection at the optical aperture surface of the light transmissive solid. 
 
 
     
     
       2. The solid state light emitting device of  claim 1 , wherein the plurality of doped semiconductor nanophosphors further comprises a doped semiconductor nanophosphor excited in response to electromagnetic energy in the range of 380-420 nm for re-emitting yellowish-green or greenish-yellow light. 
     
     
       3. The solid state light emitting device of  claim 1 , wherein the visible light output produced during the excitation of the doped semiconductor nanophosphors has a CRI of at least 80. 
     
     
       4. The light fixture of  claim 1 , wherein the visible light output produced during the excitation of the doped semiconductor nanophosphors has a CRI of at least 88. 
     
     
       5. The solid state light emitting device of  claim 1 , wherein the semiconductor chip is configured for producing electromagnetic energy of 405 nm. 
     
     
       6. The solid state light emitting device of  claim 1 , further comprising:
 at least one reflective surface within the package forming an optical integrating cavity; 
 wherein the semiconductor chip is positioned and oriented so that at least substantially all direct emissions from the semiconductor chip reflect at least once within the cavity. 
 
     
     
       7. The solid state light emitting device of  claim 6 , wherein the at least one reflective surface is diffusely reflective. 
     
     
       8. The solid state light emitting device of  claim 6 , further comprising:
 a light transmissive solid filling at least a substantial portion of the optical integrating cavity; wherein: 
 a surface of the light transmissive solid forms an optical aperture of the optical integrating cavity. 
 
     
     
       9. The solid state light emitting device of  claim 1 , wherein the plurality of doped semiconductor nanophosphors are embedded in the light transmissive solid. 
     
     
       10. A solid state light emitting device, comprising:
 a semiconductor chip for producing electromagnetic energy in a range of 380-420 nm; 
 a package enclosing the semiconductor chip; 
 at least one reflective surface forming an optical integrating cavity within the package, wherein the semiconductor chip is positioned and oriented so that at least substantially all direct emissions from the semiconductor chip reflect at least once within the cavity; 
 a light transmissive solid filling at least a substantial portion of the optical integrating cavity, wherein a surface of the light transmissive solid forms an optical aperture of the optical integrating cavity to allow emission of light from the cavity for a light output of the device; and 
 a plurality of phosphors, each of the phosphors being excited in response to electromagnetic energy in the range of 380-420 nm for re-emitting visible light of a different spectrum having substantially no overlap with absorption spectra of the phosphors, for together producing visible light in the light output of the device when the phosphors are excited by electromagnetic energy from the semiconductor chip, wherein:
 (a) the visible light output produced during the excitation of the phosphors is at least substantially white; and 
 (b) the visible light output produced during the excitation of the phosphors has a color rendering index (CRI) of 75 or higher, and 
 the semiconductor chip is positioned and oriented relative to the light transmissive solid so that any electromagnetic energy reaching the optical aperture surface of the light transmissive solid directly from the semiconductor chip impacts the optical aperture surface at a sufficiently small angle as to be reflected back into the optical integrating cavity by total internal reflection at the optical aperture surface of the light transmissive solid. 
 
 
     
     
       11. The solid state light emitting device of  claim 10 , wherein the at least one reflective surface is diffusely reflective. 
     
     
       12. The solid state light emitting device of  claim 10 , wherein the phosphors are embedded in the light transmissive solid. 
     
     
       13. The solid state light emitting device of  claim 10 , wherein the visible light output produced during the excitation of the phosphors has a CRI of at least 80. 
     
     
       14. The solid state light emitting device of  claim 10 , wherein the visible light output produced during the excitation of the phosphors has a CRI of at least 88. 
     
     
       15. The solid state light emitting device of  claim 10 , wherein the semiconductor chip is configured for producing electromagnetic energy of 405 nm. 
     
     
       16. The solid state light emitting device of  claim 10 , wherein the plurality of phosphors are doped semiconductor nanophosphors. 
     
     
       17. The solid state light emitting device of  claim 10 , wherein the visible light output produced during the excitation of the phosphors has a color temperature in one of the following ranges:
 2,725±145° Kelvin; 
 3,045±175° Kelvin; 
 3,465±245° Kelvin; 
 3,985±275° Kelvin; 
 4,503±243° Kelvin; 
 5,028±283° Kelvin; 
 5,665±355° Kelvin; and 
 6,530±510° Kelvin.